1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, a plasma display panel that has an improved structure of a display electrode to thereby enhance emission luminance.
2. Description of the Related Art
Generally, a plasma display panel (hereinafter, referred to as PDP) is a display device in which vacuum ultraviolet rays emitted from plasma through gas discharge excite phosphors to generate visible light, thereby realizing images. In a PDP, a large screen of 60 inches or more can be implemented to have a thickness of no more than 10 cm. Further, the PDP is a self-emitting device, like a cathode ray tube (CRT), and has a superior color reproduction capability, without a distortion due to viewing angle. In addition, with a simple manufacturing process, the PDP has an advantage over a liquid crystal display (LCD) or the like in view of productivity and cost and thus has been spotlighted as a next-generation industrial flat plate display and/or a home TV display.
Since the 1970's, the structure of a PDP has been evolving and, at present time, a three-electrode surface-discharge type structure is generally in use. In the three-electrode surface-discharge type structure, a front substrate has a pair of electrodes disposed on the same surface, a rear substrate is spaced at a predetermined distance away from the front substrate and has an address electrode extending to intersect (or cross-over/under) the pair of electrodes, and a discharge gas is sealed between the front and rear substrates.
In the PDP having the three-electrode surface-discharge type structure, a discharge cell to be turned on is first determined through the accumulation of wall charges on the address electrode, and a sustain discharge for displaying an emission luminance is then performed by the pair of electrodes formed on the front substrate.
In the PDP having the above structure, a discharge should be fired over a wide area, such that the discharge fired by the pair of electrodes is effectively diffused throughout the entire discharge cell. However, in the PDP according to a related art, the pair and address electrodes are disposed across the long sides of a planar-shaped discharge cell (for example, a rectangular shaped discharge cell) so as to face each other. Because of this, the discharge is fired partially along the short sides of the discharge cell and thus the discharge may not be diffused smoothly.
Also, the address electrode is made of a transparent electrode so as not to shield light from the front substrate. However, since the transparent electrode has high resistance, a metal electrode is formed on the transparent electrode in order to complement conductivity of the transparent electrode. Because light does not transmit through the metal electrode, the metal electrode is thus formed along an edge in a widthwise direction of the transparent electrode so as not to shield light from the discharge cell.
However, even when the transparent electrode and the metal electrode are formed together, the transparent electrode is disposed along the periphery of the discharge gap where the discharge occurs, which results in a high discharge firing voltage. Further, since the material (for example, indium tin oxide or ITO) for the transparent electrode is expensive, the manufacturing cost of the PDP is increased, so that the price competitiveness is lowered. Further, since the electrode formed in a strip shape on the substrate has a two-layer structure of the transparent electrode and the metal electrode, the manufacturing process is further complicated, which causes the manufacturing cost to be further increased.
On the other hand, the discharge occurring within the discharge cell is introduced by a dielectric layer, a phosphor layer, and a discharge gas between the address electrode and the pair of electrodes provided on the front substrate and thus the discharge is affected by the materials and shapes of these parts. In this case, the dielectric layer is formed to have a uniform thickness over (or under) the entire front substrate, and thus the difference in characteristic of the red, green, and blue discharge cells does not exist.
However, with regards to the phosphor layer having a blue phosphor material, such as barium-magnesium aluminate with Eu as the emission center (BaMgAl10O17:Eu), a green phosphor material, such as zinc silicate with Mn as the emission center (Zn2SiO4:Mn), and a red phosphor material, such as yttrium-gadolinium borate with Eu as the emission center (Y0.35Gd0.35BO3:EU), Y2O3:Eu, or Gd2O3:Eu; the dielectric constants of the blue, green, and/or red phosphor materials are different. Further, when manufacturing the PDP, a substantial difference in thickness according to colors may occur. Accordingly, the difference in capacitance occurs due to the characteristics of the materials of the phosphor layer and the difference in thickness, which results in a problem in that the emission luminances of the red, green, and blue discharge cells are different from each other.
In particular, if the luminance of the blue discharge cell becomes low, the color temperature (or white balance) also becomes low, and thus the brightness of the PDP is perceived by human eyes to be relatively dark. For this reason, the white balance is adjusted through a gamma correction. In this case, since the luminance of blue discharge cell is relatively low, the white balance is adjusted on the basis of the luminance of blue discharge cell. Accordingly, the loss of the emission luminance occurs through the gamma correction by that amount corresponding to the difference in luminance of blue and red (or green) discharge cells.